5.6.2 Metal: procurement and manufacture

There is increasing circumstantial evidence for Roman-period (presumably military) use of the Wanlockhead / Leadhills lead source from reappraisal of lead isotope results on lead pigs and work on pollution signatures (Hunter 2006; Mighall, unpublished). The known lead and silver source at Siller Holes, near Carlops is another circumstantial candidate given the temporary camp in its immediate vicinity and its proximity to a known road line. It is important to keep an open mind on the possibility of other metals being exploited; only iron-smelting seems to find some partial evidence, of uncertain scale (it is recorded, for instance, at Doune; Photos-Jones forthcoming).

Roman sites regularly produce iron-working evidence, as might be expected if repair (and perhaps manufacture) of tools and weapons was an everyday task. Indeed, it is now attested on campaign at the camp at Kintore (Heald 2008, 209). The nature and scale of this activity is as yet poorly understood.

Small-scale evidence of bronze-casting is found widely on fort sites, but rarely commented on (e.g. Strageath; Frere and Wilkes 1989, 203). Yet it merits synthesis to see how frequent it was present, on what scale and to what end. Surviving evidence includes examples of indigenous-style artefacts, raising the question of the nature and meaning of such items. There has been useful consideration of the alloys used in the frontier zone though scientific analysis, with Dungworth's work (1996, 1997) identifying patterns linked to technology and cultural tradition; this is an area where further testing would be valuable. Melted lead is frequently found on fort sites, and seems to have been worked regularly - presumably because it was both easy to manipulate and frequently pressed into service as a handy patching system.

More work on pollution signatures around mines would be valuable to confirm the evidence and clarify its scale: the Leadhills/Wanlockhead and Siller Holes sources are prime candidates. Were any other sources used? What iron sources were utilised? Was it simply bog ore?

Synthesis of the evidence and renewed study of surviving material to consistent standards is required. Are slag assemblages from different forts essentially similar? How do they compare to indigenous iron-working?

Synthesis of non-ferrous metalworking evidence is needed; how does copper-alloy working relate to indigenous habits?

There has been no attempt to see if the lead can tell us more; for instance, to look at source via lead isotope analysis. Is there any evidence of pewter use?